Guard against xhr.upload access in IE workers.
Guard against xhr.upload access in IE workers.

nemisj/superagent,kmalakoff/superagent-ls,deltreey/superagent,visionmedia/superagent,aaroncrows/superagent,ccapndave/superagent,mvanlonden/superagent-webpack-client,deltreey/superagent,drinks/superagent,soyuka/superagent,ertrzyiks/superagent,philipshurpik/superagent,mvanlonden/superagent-webpack-client,drinks/superagent,jarvisaoieong/superagent,eligolding/superagent,modulexcite/superagent,reinaldo13/superagent,andyburke/superagent,andyburke/superagent,craigspaeth/superagent,zsh2938/superagent,ccapndave/superagent,yussan/superagent,KingMario/superagent,simonvizzini/superagent,KuroGuo/suberagent,h1bomb/superagent,focusaurus/superagent,stanzi83/superagent,brainbytes/superagent,reinaldo13/superagent,stasha/superagent,jarvisaoieong/superagent,nemisj/superagent,yeatszhang/superagent,soyuka/superagent,focusaurus/superagent,eligolding/superagent,stasha/superagent,wushuyi/superagent,thejameskyle/superagent,noikiy/suberagent,puterakahfi/superagent,targos/superagent,alinz/superagent,philipshurpik/superagent,stanzi83/superagent,aaroncrows/superagent,yussan/superagent,thejameskyle/superagent,ertrzyiks/superagent,killerlayup/superagent,brotchie/superagent,sutoiku/superagent,RubenVerborgh/superagent,sebastianvera/superagent,yeatszhang/superagent,alinz/superagent,RubenVerborgh/superagent,modulexcite/superagent,KuroGuo/suberagent,geminiyellow/superagent,killerlayup/superagent,puterakahfi/superagent,zsh2938/superagent,fredigato/superagent,kmalakoff/superagent-ls,brotchie/superagent,visionmedia/superagent,noikiy/suberagent,visionmedia/superagent,targos/superagent,geminiyellow/superagent,wushuyi/superagent,brainbytes/superagent,craigspaeth/superagent,KingMario/superagent,sebastianvera/superagent,simonvizzini/superagent,sutoiku/superagent,h1bomb/superagent,fredigato/superagent